Block Copolymer at Nano-Patterned Surfaces

Abstract

We present numerical calculations of lamellar phases of block copolymers at patterned surfaces.We model symmetric di-block copolymer films forming lamellar phases and the effect of geometrical and chemical surface patterning on the alignment and orientation of lamellar phases. The calculations are done within self-consistent field theory (SCFT), where the semi-implicit relaxation scheme is used to solve the diffusion equation. Two specific set-ups, motivated by recent experiments, are investigated. In the first, the film is placed on top of a surface imprinted with long chemical stripes. The stripes interact more favorably with one of the two blocks and induce a perpendicular orientation in a large range of system parameters. However, the system is found to be sensitive to its initial conditions, and sometimes gets trapped into a metastable mixed state composed of domains in parallel and perpendicular orientations. In a second set-up, we study the film structure and orientation when it is pressed against a hard grooved mold. The mold surface prefers one of the two components and this set-up is found to be superior for inducing a perfect perpendicular lamellar orientation for a wide range of system parameters.

Tailoring Nanostructures Using Copolymer Nanoimprint Lithography

“…L 0 ( Figures a,b) were observed, oriented parallel to the groove edges over tens of micrometers. Self‐consistent field theory (SCFT) calculations19, 20 (see Supporting Information) in a three‐dimensional geometry mimicking the experimental substrate and mold (Figure 1) support the experimental findings and are shown in Figure . This agreement between theory and experiment strengthens our claim that, in this low‐temperature case, the observed overall orientation is determined by the surface energy.…”

Block Copolymer Morphology Formation on Topographically Complex Surfaces: A Self‐Consistent Field Theoretical Study

“…As expected, lamellae parallel to the substrate are preferred as the substrate affinity increases. The transition from perpendicular lamellae to parallel lamellae occurs when the affinity is close to 0.0 with a flat substrate, which is consistent with previous studies; however, the transition moves to higher preferential surface area with a step‐like substrate. Specifically, the transition occurs when the affinity is about 0.50 for the trench‐like substrate with 1.0 L o width, and the transition is further delayed as the trench narrows (as shown in Figure ).…”

“…The step width is assumed to be the same as that of the trench. When the film thickness is an integer or half‐integer multiple of the periodic spacing of the diblock copolymer, the parallel morphology is more likely to be formed between a neutral top surface and a bottom surface that favors a particular block of the block copolymer . Therefore, in our study, the film thickness was set at 1.50 L o from the bottom of the trench, unless otherwise noted.…”

Block copolymer films with free interfaces: Ordering by nanopatterned substrates

“…As is known from previous works [21][22][23], symmetric BCP in the bulk have a transition between a disordered phase above the Order-Disorder temperature (ODT), N χ c ≃ 10.5, and a lamellar phase of natural periodicity l 0 , below the ODT. The numerical procedure, i.e.…”